Multicomponent fibers are, in and of themselves, well known and have been used extensively to achieve various fiber properties. For example, multicomponent fibers have been formed of two dissimilar polymers so as to impart self-crimping properties. See, e.g., U.S. Pat. No. 3,718,534 to Okamoto et al. and U.S. Pat. No. 4,439,487 to Jennings. Multicomponent fibers of two materials having disparate melting points for forming point bonded nonwovens are known, for example, from U.S. Pat. No. 4,732,809 to Harris et al. Asymmetric nylon-nylon sheath-core multicomponent fibers are known from U.S. Pat. No. 4,069,363 to Segraves et al.
One problem that is encountered when multicomponent fibers are formed having distinct domains of dissimilar polymers which are incompatible with one another is that the domains often separate at the boundary between the domains. This separation results in fracturing or splitting of the fiber thereby weakening the system (e.g., yarn, fabric, carpet or like textile product) in which the fiber is used. Weakening of the fiber system can be sufficiently acute to prevent the system from undergoing downstream processing (e.g., drawing, texturing, heat-setting, tufting, knitting, weaving and the like). Furthermore, such fracturing and/or splitting of the fibers can result in poor product qualities, such as poor appearance and poor wear performance.
It would, therefore, be highly desirable if multicomponent fibers having distinct longitudinally coextensive polymer domains formed of incompatible polymers could be produced which have minimal (if any) inter-domain fracturing and/or splitting. It is toward providing such a fiber and method of producing the same that the present invention is directed.
Broadly, the present invention is directed to a multicomponent fiber and a method of producing the same whereby an inter-domain boundary layer is interposed between distinct domains formed of incompatible polymers so as to minimize (if not eliminate entirely) separation of the domains at their interfacial boundary. The polymer forming the inter-domain boundary layer therefore is provided so as to be compatible with the otherwise incompatible polymers forming each of the domains between which it is interposed.